The present invention generally relates to a magnetoelectronics, and more particularly to a magnetoelectronics element.
Magnetoelectronics, spin electronics and spintronics are synonymous terms for the use of effects predominantly caused by electron spin. Magnetoelectronics is used in numerous information devices, and provides non-volatile, reliable, radiation resistant, and high-density data storage and retrieval. The numerous magnetoelectronics information devices include, but are not limited to, magnetic random access memory (MPAM), magnetic sensors and read/write heads for disk drives.
Generally, a magnetoelectronics information device is constructed with magnetoelectronics elements (e.g., giant magneto resistance (GMR) elements or tunneling magneto resistance (TMR) elements). Efforts are continually made to reduce the size of magnetoelectronics elements in order to increase package density. While magnetoelectronics elements tend to operate effectively and efficiently as size is decreased, some problems arise with size reduction.
Without intending to be bound by theory, as the volume of a magnetoelectronics element is reduced, the energy barrier to the element switching approaches the thermal energy, and data retention is lost. This problem may be addressed with the maintenance of a substantially constant element volume through increased element thickness and lateral dimension reduction. However, there are factors that limit element thickness.
For a given lateral size of an element, there is an element thickness above which the net magnetization is decreased or completely lost due to formation of a flux closing configuration or magnetic vortex having no net moment. (See, R. P. Cowburn et al., Physical Review Letters, Volume 83, Number 5, pages 1042-1045, Aug. 2, 1999). This magnetization loss is typically undesirable in magnetoelectronics elements, as proper device operation usually relies upon uniform uniaxial magnetization. Also, relatively high magnetic fields are needed to annihilate magnetic vortices.
In addition to magnetic vortex formation, the element thickness affects the switching behavior of the element. This influence of the elements geometrical shape on element switching behavior is due in part to the demagnetization field effect (i.e., the tendency for electron spins to align parallel to a boundary or edge of an element). As the thickness of the element is increased, the demagnetization field effect increases and domain nucleation has a greater negative affect on the switching behavior. Specifically, domain nucleation undesirably encourages spin reversal when an external field is applied to the element for switching. This reversal does not involve the entire bit volume, thereby reducing the energy barrier to switching. Preferably, the switching behavior of the element is a substantially coherent rotation of all electron spins with minimal nucleation allowing the full volume to participate.
Accordingly, it is desirable to reduce the size of magnetoelectronics elements while maintaining a sufficient energy barrier for data retention. In addition, it is desirable to minimize magnetic vortex formation and domain nucleation in magnetoelectronics elements. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.